In various fields of car bodies and parts, as well as household electric appliances, steel products, steel furniture, construction materials and construction machines, epoxy type cationic electrodeposition coating compositions capable of forming coat films having high corrosion resistance are widely utilized. Recently, in the field of car industry, the coating compositions are needed to form coat films having much improved corrosion resistance. In addition, the coat films are strongly desired to have much improved chipping resistance and low temperature properties.
Under the situation, improvement and investigation of coating compositions of containing various flexible components have been made in these days. For instance, Japanese Patent Publication No. 41670/81 has proposed use of butadiene-acrylonitrile copolymers; and Japanese Patent Kokai No. 254732/89 has proposed incorporation of an urethanediol into a chain extender of an epoxy resin. The proposed techniques would be effective for improving the flexibility of the coat films, but they are still insufficient for improving the adhesiveness of the coat films to metal substrates, especially the adhesiveness at a low temperature, and the chipping resistance of them.